Linear polymers of high molecular weight, including polydiorganosiloxanes as well as various organic polymers are known as effective agents for improving the flow, spreadability, wear resistance and other characteristics of liquid media, such as polishes, cosmetics, and the like. Also known is their ability to increase the flow of crude oils and refined petroleum products through pipelines. See, for example, Canevari et al, U.S. Pat. No. 3,493,000; Martellock, U.S. Ser. No. 72,193, filed on Sept. 14, 1970, and assigned to the assignee of the present application; White et al., U.S. Pat. No. 3,215,154; Gibson, U.S. Pat. No. 3,351,079; Seymour et al., U.S. Pat. No. 3,559,664; British Pat. No. 1,319,098; Cutler et al., U.S. Pat. No. 3,692,676; and Kruka et al, U.S. Pat. No. 3,687,148.
It is well known that such high polymers as drag reduction additives must be in solution in the liquid media, e.g., a flowing liquid hydrocarbon, e.g., crude or refined oil, in order to be effective. However, the practical attainment in the liquid media of homogeneous solutions of suitable concentration, typically 10-2000 ppm of polymer, has heretofore presented serious engineering and economic problems. Polymers of the required high molecular weight are hard gums, slow to dissolve, and direct injection of bulk polymer is completely impractical.
To date in laboratory and field tests, with pipeline fluids, it has proven convenient to inject previously prepared "master batch" solutions in hexane, kerosene, and the like. However, at levels of full scale use, which approach millions of pounds of additive annually, serious problems arise in the production, shipment and storage of such solutions.
One basic problem is the very high viscosity of master batch solutions, because of the necessarily high molecular weight of the drag-reducing polymer. Above a concentration limit of about 5 percent, the viscosity becomes so high that such solutions become impractical for injection pumping, and also very difficult to produce at uniform and controlled concentration. The cost of purchase and shipment of such large amounts of solvent in relation to active polymer is a serious burden.
A second basic problem is that the process of dissolving the hard gums ordinarily employed is inherently lengthy and expensive. Agitative intensity must be kept low to avoid shear degradation of the dissolved polymer to shorter chains, because these are ineffective as drag reducers. This requires costly investment in very bulky equipment of unconventional type.
Although it is possible to ship the polymer in bulk and to convert it to master batch at the injection site, typically using part of the pipeline contents as "free" solvent, in practical terms, the number of separate dissolving machines becomes prohibitive. Users strongly prefer instead to employ a formulated product ready for injection, rather than to be encumbered with dissolving operations.
It has previously been proposed that a more convenient drag reduction product might be made by milling bulk high polymer resin into fine particles, which will dissolve more readily. These, however, tend to reagglomerate on standing, and means of preventing reagglomeration have not been found. Further, in all processes involving mechanical disintegration of bulk resin, whether or not in the presence of a second, non-solvent liquid phase (for example by milling, colloid milling, homogenizing, and the like), there is grave risk of shear degrading the polymer.
It has now been discovered that novel two-phase compositions of liquid media modifying and drag-reducing polymers can be produced, and these overcome all of the above-mentioned problems. Basically, each such composition consists of a disperse phase of fine particles of drag-reducing polymer, suspended in a continuous liquid phase comprising a non-solvent for that particular polymer. As a further requirement, the compositions of both disperse and continuous phase are so selected as to be soluble in the hydrocarbon media (the pipeline stream.)
The new compositions of this invention have the following advantages:
(1) They can contain as much as 50 percent or more of drag-reduction effective polymer at readily pumpable consistencies.
(2) In preferred cases, and according to one aspect of the invention, the polymer can be formed in situ as the final disperse phase, with very significant elimination of processing steps and degradation hazard.
(3) The laborous operation of dissolving high polymer, and the need for using large volumes of solvent are entirely eliminated.
In addition, they appear to be longer acting than prior art compositions. This seems to result from the fact that under pipeline flow conditions, only dissolved polymer suffers shear degradation; suspended particles are immune. The smallest particles dissolve most rapidly, while larger droplets dissolve more gradually during passage along the pipeline. This results in continuous replenishment of the longest, most effective molecules in solution, directly offsetting any loss due to shear degradation. With adequate control of particle size distribution, benefits approximately those of multiple injection sites along the line can be obtained with the economy of a single injection. This controlled rate of solution principle bears a partial analogy to the 12 hour cold capsule, which releases medication slowly.